1. Field of the Invention
This invention relates to a printing ink which contains an active agent or agents. More particularly, the invention relates to an active agent-containing printing ink which can be used for printing articles made of synthetic resin as well as other various goods made of paper, cloth, leather, wood or bamboo, china or porcelain, glass and metals, and wall surfaces of rooms.
The active agent-containing printing ink of the present invention is characterized in that the effect of active agent contained therein can be properly controlled and can be maintained for a long period of time.
2. Description of the Prior Art
In the conventional art, perfumes or other functional chemicals (hereinafter referred to as "active agents") are sometimes blended into printing ink in order to give the effect of active agent on printed goods.
In Japanese Laid-Open Utility Model Publication No. 62-572, it is disclosed that a chemical agent is directly mixed into a printing ink. Japanese Laid-Open Utility Model Publication No. 61-102598 and No. 61-103324 disclose that a chemical agent which is included in cyclodextrin is mixed in printing ink. Japanese Patent Publication No. 51-15769 discloses the use of chemical agents which are adsorbed by a porous substance or contained in microcapsules.
U.S. Pat. No. 4,515,849; Keino et al., teaches a printing ink which can be formulated form a high polymer thermoplastic resin. However, Keino reference relates to a transfer printing sheet which comprises a base sheet such as cellulose fiber paper, a releasing resin layer, a pattern layer and a dissolving agent layer. The art is similar to that of the above Japanese Laid-Open Utility Model Publication No. 62-572 wherein a chemical agent is mixed directly into printing ink. This reference does not teach the utilization of a thermoplastic polymer as a carrier impregnated with the active agent and then mixing the active agent-containing thermoplastic polymer into printing ink.
There have been, however, several problems in that, when an active agent is directly mixed into a printing ink, the active agent is liable to be evaporated and released during printing operation, which fact shortens the effective life of the active agent. In the case that cyclodextrin is used, full effect of the active agent is hardly produced because most part of the active agent remains as included. In the method to use a porous substance, the effective life is not long enough. In the microcapsule method, it is necessary to rupture the microcapsules in order to produce the effect of active agent.
In order to solve the above problems in the prior art, the inventors of the present application have made extensive investigations, and as a result, the present invention has been accomplished.